Backing up with a dolly attached and no one to assist in that job is probably not impossible but sure come comes close. The shorter the trailer the more difficult it is to back up. If I recall the Mariner is a heavy vehicle. Does the Karkaddy have that much capacity and does it have brakes? I would sure like to tow 4 down as a single traveler. All I need to do is get close and the adjustable arms on the tow bar let me hook up by myself. Now that I have the Roadtrek I don't need the toad but will with the GMC. I also travel alone.